This project involves studies on the possible sex difference in response to the colon carcinogens, 1,2-dimethylhydrazine (DMH) and azoxymethane (AOM) and studies on mutagenicity of urine after feeding chemical carcinogens. In the female F344 strain rats, DMH produced few colon carcinomas; however, AOM induced colon tumors and also kidney tumors. Male F344 rats were susceptible to tumor induction after treatment with both DMH and AOM at low levels and with short latent period. Carcinogens and their metabolites in the urine were tested for mutagenicity using the Salmonella typhimurium system. Modification of the urinary mutagenicity was tested with an inhibitor of carcinogenesis such as acetanilide, tyrosine and selenium.